1. Field of Invention
The present invention relates to a variable posture work chair, particularly a component system in use at, or designed to function as, an office, industrial, or home work station.
2. Description of Prior Art
A widespread crisis in the physical aspect of sitting at the modern work station has initiated a variety of so-called ergonomic attempts to solve the problem. Briefly stated, that problem arises out of improper seating posture and the extended immobilization that is required of a worker at a work station, particularly where a keyboard is in use. Worker pain usually manifests itself in the lower back, the legs, the neck, the shoulders and the wrists. Much, although not all, of this pain can be attributed to poorly designed chairs that do not allow the sitter to effect real and meaningful changes in the long term sitting position.
Efforts to solve the problem from the standpoint of seating at the work station can be loosely grouped into five broad categories: conventional office chairs, kneeling posture chairs, forward support chairs, variable posture chairs and dedicated personal work stations. We shall omit from this discussion stools and associated designs that support a person in a standing or near standing position.
"Conventional office chairs" are what we are mostly accustomed to, comprising a base, a seat, a backrest, appropriate mechanisms and, in some cases, rests for the head and arms. Depending upon the design variation, the seat and the backrest may be solidly connected to act as a unit or they may move and/or be adjusted somewhat independently of one another. U.S. Pat. No. 5,056,866 to Tobler shows a conventional office chair incorporating another possible design feature, that of a rocker; Tobler builds his seat and back as a solid unit. It should be noted that the rocker principle can also be used in the above design of independent back and seat movement.
Most office chairs sold are of the conventional variety, improvements to which focus mainly on more and better chair adjustments, better seat design, and provision for lumbar support. The intrinsic drawback here is that the sitter is limited to minor variations on one basic sitting position, that of leaning backward; when the worker leans forward and into his or her work, as most people do, they come into opposition to the chair's basic design, eventually stressing the entire body. In such a chair one typically sits up or forward on the seat for brief periods of time, periodically collapsing against the chair's backrest for relief. Long term sitters resort to unconscious fidgeting, a sign the body is seeking a new position. Even those variations that allow the seat to tilt forward to accommodate the shifted pelvis are extremely limited because they do not provide support for the forward leaning body.
"Kneeling posture chairs" are a group of chairs that typically have a forward tilted seat, an oppositely tilted knee rest(s), and may be mounted on a variety of bases. U.S. Pat. No. 4,328,991 to Mengshoel and Opsvik, U.S. Pat. No. 4,589,699 to Dungan, and U.S. Pat. No. 4,767,159 to Opsvik are examples of this type of seating arrangement. While these chairs offer some improvement by emphasizing a forward tilted pelvis and an erect spine, they have several major drawbacks. First, because of the inclined seat angle and gravitational forces the sitter tends to slide forward and off of the seat, being prevented from doing so only by the knee rest. This design inherently focuses constant pressure directly on the knees, resulting in intolerable pain for many people. Second, while a desirable and ergonomically correct sitting posture would involve relaxing the legs while spreading out any support pressure on them evenly from the knee to the ankle, this inherently focused knee pressure makes such posture impossible. Third, while the design is supposed to promote good posture without upper body support it works only marginally in practice. A person at a work station does not sit eternally erect; one is constantly leaning forward, backward and to the sides, placing stress on the very muscles which maintain erect posture. As these muscles fatigue the sitter begins to slump and the posture actually deteriorates. Fourth, while the basic posture these chairs create is a good starting place, it is the only one they offer; immobility and constriction are serious problems with these chairs and many people abandon them after a few months of use. (One configuration shown in U.S. Pat. No. 4,328,991 does include a backrest and rails to allow a rocking motion; this chair will be mentioned again below as a variable posture design.)
"Forward support chairs" represent an attempt to solve a fundamental problem in work place sitting: that of accommodating the forward lean of the body. U.S. Pat. Nos. 4,650,249 to Serber and 4,943,117 to Brown show non-reversible forward support while sitting; U.S. Pat. Nos. 3,165,314 to Clearman and Webster and 3,754,787 to Garber show additional non-reversible industrial applications of this principle. Supporting the forward lean has certain advantages, but the design is still limited to one basic seating posture; it is also subject to certain of the criticisms of the reversible chairs below.
"Variable posture chairs" are here considered to be any chair that can support at least two distinct changes in body position. The significant advantage of this approach is that the sitter is allowed a complete posture change. We will form two subcategories in this group: reversible chairs and hybrids. Reversible chairs are chairs that can function in a conventional fashion and also be turned around to offer forward support. U.S. Pat. Nos. 454,100 to Wilson, 2,364,050 to Benson, 4,607,882 to Opsvik, and 4,832,407 to Serber show true reversible chairs, wherein the sitter may lean either forward or backward against a vertical plane of support. Variations of this and the aforementioned forward support principles can offer significant advantages at the work station; however, with the possible exception of the dedicated industrial designs all of these chairs also have significant drawbacks. First, since an adequate backrest must be large enough to comfortably spread out the pressure on the rear of the rib cage, reversal offers a large torso/chest support by default rather than planned design, or it compromises both; second, reversal cannot adequately address the real structural and physiological differences between forward and backward leaning; third, it can be argued that abdominal support is, in many cases, a preferable method of forward support; fourth, the torso support is mounted on a center post that comes up directly between the legs; therefore, they must be straddled to get into, and fifth, in the case of the reversible designs a sitter must get up and out of the chair, physically reverse it, and sit back down again to gain the benefit of that design.
These factors make the design singularly unattractive for many people to use in an office environment, and impossible for a woman wearing a dress. The center post mounting of the torso support is a particular nuisance. Several of these design issues also make it extremely difficult for those who may need help the most--the injured and the infirm--to enjoy its benefits.
Hybrids include any variable posture chair not already mentioned. Such chairs generally offer some knee/leg support in the form of a cushioned rest mounted to the chair base of a design that includes a seat and a backrest; the familiar recliner design would be part of this category. In U.S. Pat. No. 4,832,407 Serber has attached a knee rest to the center post of a traditional five star chair base via an extended member; only Serber offers optional forward support within this group. In U.S. Pat. No. 4,765,684 to Kvalheim and Petersen a knee rest is mounted to the center post of a conventional chair base via an extended member which allows it to be folded up and out of the way. In U.S. Pat. No. 5,054,857 to Kvalheim the back of a conventional chair may be folded down to become a knee rest, yielding a kneeling posture design. In U.S. Pat. No. 4,767,160 to Mengshoel a knee rest is mounted onto the tips of a five star base as an optional extension for a conventional chair. A somewhat different arrangement is shown in U.S. Pat. No. 5,255,957 to Opsvik and Mengshoel. As noted, Mengshoel and Opsvik also suggest a hybrid in U.S. Pat. No. 4,328,991, allowing the user of a kneeling posture chair to lean back in a conventional fashion and create a rocking motion. In U.S. Pat. No. 5,186,519 to Larson conventional and kneeling postures are suggested.
A major disadvantage to U.S. Pat. Nos. 4,832,407, 4,765,684 and 5,054,857 is that the extended member used to mount the knee/leg rest juts out directly between the legs, thus posing an eternal obstruction for the sitter's legs and feet; additionally, such a design approach does not provide for maximum chair stability. In U.S. Pat. Nos. 4,767,160 and 5,255,957 the leg obstruction is marginally lessened and stability increased, but in both cases an undue amount of non-integrated hardware is employed to stabilize a traditional five star base. In U.S. Pat. No. 5,255,957 Opsvik further suggests limited variable posture by employing a unique system of additional hardware; both Opsvik and Mengshoel show designs utilizing a solidly connected back-seat-armrest configuration. U.S. Pat. No. 4,328,991 is basically a variation on the kneeling posture design. In U.S. Pat. No. 5,186,519 Larson attains leg clearance and stability, but at a price of hardware and mechanization. Larson also shows variable posture by turning a seat into a backrest, but as with the reversible chairs the sitter must arise and change position to gain the benefit of the design.
"Dedicated personal work stations" are, in general, seating arrangements resembling a school desk designed to accommodate the worker and the personal computer. U.S. Pat. Nos. 4,880,270 to Cooper, 4,925,240 to Peters, 5,022,706 to Bryan, 5,054,852 to Tholkes and 5,056,864 to Cooper are examples of this approach; 4,767,159 to Opsvik shows an auxiliary desk mounted to the knee rest of a kneeling posture chair; U.S. Pat. No. 5,169,210 to Fricano shows a keyboard desk mounted to the center post of a conventional chair.
All of these examples but U.S. Pat. Nos. 4,767,159 and 5,169,210 are, by definition, dedicated stand alone designs. While this approach certainly has some merit it prevents the design from being used with a larger free standing work station, a definite commercial drawback. And while a proper design approach would integrate true variable posture for the worker into a keyboard work station, only Cooper's imaginative U.S. Pat. Nos. 4,880,270 and 5,056,864 really attempt to do this. Clearly, the design awaits further development.
The evolving demands of the modern work station overwhelm the human body. Days grow into months and years of sitting; the body grows, ages, changes, gets sick, injured or pregnant, and, above all, tires of sitting in the same position. The fact that the conventional chair is the most successful and widely used design in the world today should not obscure its increasingly obvious limitations. Looking elsewhere, all of the alternative designs mentioned above offer certain improvements but only as parts of the puzzle; individually they fail to provide a complete solution. What is needed is a simple, user friendly design that improves upon and integrates all of these elements--and some new ones--into a new, synergistic seating device, preferably one that can be built, marketed and used as a component system.